It is known to use compounds which contain from two to six OH groups and have a molecular weight of from 62 to about 10,000 for preparing polyurethanes. The following are examples of such polyhydroxyl compounds: simple polyhydric alcohols, e.g. ethylene glycol, diethylene glycol, hexane diol, glycerol, trimethylol propane. Further examples include higher molecular weight polyethers, polythioethers, polyesters and polyacetals. These higher molecular weight polyhydroxyl compounds are prepared from low molecular weight units in known manner. These hydroxyl compounds generally have only a low polarity and carry no other functional groups.
For preparing foams from polyisocyanates and polyhydroxyl compounds, it is generally necessary to use surface active compounds, especially organopolysiloxanes. These substances have an emulsifying action on the reactants and stabilize the foam structure which initially is still liquid. Emulsifiers are occasionally also used for the production of non-cellular polyurethanes if the reactants are insufficiently compatible or if fillers are used. In many cases, the emulsifier or stabilizer must be added as a separate component to the reaction mixture, which may entail problems of dosing because of the small quantities in which these components are generally used.
It would be advantageous if, for example, in the case of incompatibility of the reactants, it would be possible to dispense with the use of particular surface active compounds because the polyols used already have the desired surface active properties. There is therefore a need for polyols having surface active properties. Moreover, there is a demand for polyols which are hydrophilic and have a relatively high polarity so that they will have better compatibility with water and so that the foams produced from the polyols will have a certain water absorption capacity, as well as improved resistance to solvents. There is also a demand for polyhydroxyl compounds which yield polyurethanes having improved fire characteristics. Lastly, it would be desirable to have OH prepolymers available which do not give rise to toxic aromatic diamines when they undergo hydrolytic degradation.
The present invention provides a solution to these problems.